Endocrine Abstracts

An 85-year-old woman attended the endocrine clinic with hypercalcaemia and raised PTH levels. Her background included breast cancer treated with bilateral mastectomy and hormone therapy 3 years previously, with no evidence of disease on imaging 2 years previously. On attendance, her clinical examination was unremarkable, with no palpable neck mass. Biochemical investigations showed: Adj Ca 3.12 mmol/l, PTH 45.0 pmol/l, PO4 0.94 mmol/l, ALP 119U/l, Alb 45g/l, 25-OH Vit D 15.7 nmol/l, eGFR 47, calcium excretion index 0.097 mmol/l. A Sestamibi scan was consistent with a left-sided parathyroid adenoma. She was initially treated with 60mg cinacalcet, however became intolerant to this, with refractory symptomatic hypercalcaemia (Adj Ca 3.27 mmo/l) and acute kidney injury (eGFR 20). She subsequently underwent emergency parathyroid surgery, with resection of a 4cm left-sided adenoma and left hemi-thyroidectomy en bloc, due to intraoperative suspicion of parathyroid carcinoma. Interestingly, the histology was consistent with metastatic breast cancer within a parathyroid adenoma. Following initial normalisation of calcium levels, she was readmitted with hypercalcaemia (Adj Ca 3.08 mmo/l) and suppressed PTH (1.0 pmol/l). A CT thorax, abdomen, and pelvis identified lung and liver metastasis, however skeletal metastases were absent on bone scintigraphy, suggesting a diagnosis of humoral hypercalcaemia of malignancy. MDT discussion confirmed a diagnosis of metastatic breast cancer and recommended palliative management. Metastases to the parathyroid are present in 12% of patients with disseminated cancer on autopsy, with breast the commonest site of origin. Tumour-to-tumour metastasis within the parathyroid is much rarer and its incidence is unclear. Interestingly, endocrine tumours including parathyroid adenomas, account for 45% of recipient tumour-to-tumour spread, possibly due high vascularity. This rare case of tumour-to-tumour metastasis of breast primary within a parathyroid adenoma, illustrates the importance of considering dual pathology, in patients with hypercalcaemia and a background of malignancy.